The diver went into the deep water beyond the danger limit.

潜水员下潜到超过危险线的深水中去了。

《新英汉大辞典》

And Kai, you are a deep-sea diver.

凯，你是一位深海潜水员。

youdao

I mean it's the color of night, it's the color of the ocean and as a scuba diver I've spent a lot of time looking into the deep blue, the pelagic blue.

这是夜晚的颜色，是大海的颜色，我喜欢潜水，常花许多时间观察海洋中的深蓝色，这是深海的颜色。

youdao

We're reminded that the "Titanic" director is an avid deep-sea diver: Pandora's rainforest resembles a spectacular coral reef.

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This is relatively deep for the average leisure diver and the wrecks should ideally be visited only by professional divers with experience.

UNESCO: Underwater Cultural Heritage